The present invention is generally directed to improvements in the color video processing art. More particularly, the present invention is directed toward providing improved circuitry for providing drive adjustment control for a video output stage as may be used in a wideband RGB video processor.
In television and other color video monitor applications, a color video signal typically comprises red (R), green (G), and blue (B) components. A received signal typically may be separated into R, G and B components, amplified and then applied to appropriate R, G and B inputs of a cathode ray tube (CRT) color display terminal for visual display. Also, gain, contrast and sometimes black level controls commonly may be provided for customer adjustment of the displayed video signal.
Various applications, including those in which computers contain drive circuits that interface with CRT display devices, create a desirability for the amplifying, or RGB video processing, stage to operate efficiently and accurately through a wide band of video frequencies which may be encountered. Accordingly, it is desirable to provide a wideband RGB video processor for use in color televisions and color video monitors.
However, efforts to provide a wideband RGB processor may frequently be frustrated by an undesired limiting effect on the signal slew rate caused by the relatively large voltage swings in a typical video signal.
Further, it is desirable to provide a feedback control circuit for video monitors for stabilizing the black level of the video display in overcoming other signal distortions which may be incurred during RGB processing. Such variations or distortions may be induced by the gain control circuit, or temperature fluctuations or other extraneous distortions which may be induced by component value fluctuations.
Additionally, individual CRT display terminals may vary as to their phosphorous content or other individual characteristics. Accordingly, it is desirable to provide for means for obtaining the correct balance of the AC component of the final video output signal. The correct ratio is typically particular to individual CRT. Accordingly, a factory controlled adjustment may be optimally desirable.
Thus, a principal object of the present invention is to generally overcome deficiencies which exist in the prior art and to provide an improved RGB video processor.
It is a further object of the present invention to provide a drive adjustment control for video output stage to provide for adjustment of the input-output voltage gain of the AC component of the video signal.